Apparatus and method for receiving digital television signal with backward compatibility byte

ABSTRACT

Provided are a Vestigial Side Band (VSB) digital television (DTV) receiver based on is A/53 of the Advanced Television System Committee (ATSC) that can secure backward compatibility of a low-ranked DTV receiver by using parity bytes added to robust data for error correction and obtain RS coding gain from the robust data, and a method thereof. The DTV receiver includes: a receiving unit for receiving a transmission signal including general data and robust data and converting the transmission signal into a base-band signal; an equalizer for determining a symbol level of the transmission signal; a trellis decoder for performing trellis decoding on a symbol of the determined level; a nonsystematic Reed Solomon (NRS) decoder for performing NRS decoding on the trellis-decoded robust data and correcting an error; and a restoring unit for restoring a digital video data stream with respect to the trellis-decoded general data and the NRS-decoded robust data.

CROSS-REFERENCES TO RELATED PATENT APPLICATIONS

The present application claims priority under 35 U.S.C. 119(a) to Koreanapplication number 10-2004-0022643, filed on Apr. 1, 2004, and Koreanapplication number 10-2004-0064329, filed on Aug. 16,2004, in the KoreanPatent Office, both of which are incorporated herein by reference intheir entirety as if set forth in full.

TECHNICAL FIELD

The present invention relates to a Vestigial Side Band (VSB) digitaltelevision (DTV) receiver based on a DTV Standard, which is A/53 of theAdvanced Television System Committee (ATSC), and a method thereof.

BACKGROUND ART

The standard of the Advanced Television System Committee (ATSC) suggeststo use a signal obtained by modulating 12 independent data streams,which are trellis encoded and time-multiplexed, into 10.76 MHz-rate8-level Vestigial Side Band (VSB) to transmit High Definition Television(HDTV) broadcasting through a terrestrial broadcasting channel. Thefrequency band of the signal is transformed into a frequency band of 6MHz which corresponds to a standard Very High Frequency (VHF) orUltrahigh Frequency (UHF) terrestrial television channel. Signals of thecorresponding channel are broadcasted at a data rate of 19.39 Mbps persecond. Detailed technology on the ATSC DTV standards and A/53 arereadily available through the ATSC.

However, transmission signals of a conventional 8-VSB transceiver aredistorted in indoor and mobile channel environments due to variablechannel and multipath phenomena, and this degrades reception performanceof the receiver.

In other words, transmitted data are affected by various channeldistortion factors. The channel distortion factors include a multipathphenomenon, frequency offset, phase jitter and the like. To compensatefor the signal distortion caused by the channel distortion factors, atraining data sequence is transmitted every 24.2 ms, but a change inmultipath characteristics and Doppler interference exist even in thetime interval of 24.2 ms that the training data sequences aretransmitted. Since an equalizer of the receiver does not have aconvergence speed fast enough to compensate for the distortion ofreceiving signals, which occurs by the change in multipathcharacteristics and the Doppler interference, the receiver cannotperform equalization precisely.

For this reason, the broadcasting program reception performance of 8-VSBDTV broadcast is lower than that of an analog broadcast and reception isimpossible in a mobile receiver. Even if reception is possible, there isa problem that a signal-to-noise ratio (SNR) satisfying Threshold ofVisibility (TOV) increases.

In order to resolve the above problem, a dual stream transmission methodwhere a DTV transmission signal is transmitted by separating generaldata and robust data is discussed recently. In other words, researchersseek to improve the performance of a DTV receiver by adding robust datawhich are less sensitive to external interruption to general data andtransmitting the robust and general data together.

FIG. 1 is a block diagram showing a conventional DTV transmitter. Asshown, the transmitter 100 includes: a first multiplexer 101, a datarandomizer 103, a Reed Solomon (RS) encoder 105, a robustinterleaver/packet formatter 107, a data interleaver 109, a robustencoder 111, a robust data processor 113, a trellis encoder 115, asecond multiplexer 117, and a pilot adder/modulator/Radio Frequency (RF)converter 119.

The first multiplexer 101 multiplexes, a general data packet 121 and arobust data packet 123.

The general data packet 121 and the robust data packet 123 are serialdata streams formed of 188-byte Moving Picture Experts Group (MPEG)compatible data packets, and they are inputted into and randomized inthe randomizer 103 and 20-byte parity information is added thereto forForward Error Correction (FEC) in the RS encoder 105.

Subsequently, the robust interleaver/packet formatter 107 performsinterleaving on the robust data and secures space for inserting a robustdata header and a parity bit.

The packet-formatted robust data and the RS-encoded general data areinterleaved in the data interleaver 109 and inputted into the robustencoder 111.

The robust encoder 111 and the trellis encoder 115 maps the inputtedgeneral and robust data to any one symbol level among{−7,−5,−3,−1,1,3,5,7}.

Meanwhile, the robust data processor 113 adds 20 parity bytes byperforming RS encoding on the packet-formatted robust data to maintainlow-rank compatibility with a conventional DTV receiver that does notsupport robust data.

The trellis-encoded general and robust data are combined with segmentsynchronization and field synchronization bit sequences from asynchronization unit (not shown) in the second multiplexer 117 tothereby generate a transmission data frame. Subsequently, a pilot signalis added thereto in a pilot adder. A symbol stream is modulated intoVSB-suppressed carrier wave in a VSB modulator. A base-band 8-VSB symbolstream is finally converted into an RF signal in an RF converter.

The DTV receiver restores an MPEG data stream by carrying out a processreverse to the process of the transmitter on the transmitted signal.

A receiver that supports only general data can maintain backwardcompatibility by processing inputted robust data as null packets.

Also, a receiver capable of robust data can improve performance inreceiving general and robust data entirely by raising a convergencespeed of an equalizer and improving the performance of a trellisdecoder.

As described above, fine reception performance can be expected even in apoor transmission environment by mixing general data with robust dataand transmitting them in the form of dual stream.

However, the above-described DTV transmission system uses the paritybytes, which are obtained by performing RS coding on robust data andadded, only for the backward compatibility of a low-ranked receiver andit does not use them for the purpose of error correction.

If the parity bytes added to the robust data can be used for the errorcorrection, the robust data reception performance can be improvedfurther.

Disclosure

Technical Problem

It is, therefore, an object of the present invention to provide aDigital Television (DTV) receiver that can secure backward compatibilityof a low-ranked DTV receiver by using parity bytes added to robust datafor error correction and obtain RS coding gain from the robust data, anda method thereof.

The other objects and advantages of the present invention can beunderstood by those of ordinary skill in the art from the drawings,detailed description, and claims of the present specification.

Technical Solution

In accordance with one aspect of the present invention, there isprovided a Digital Television (DTV) receiver includes: a receiving unitfor receiving a transmission signal including general data and robustdata and converting the transmission signal into a base-band signal; anequalizer for determining a symbol level of the transmission signal; atrellis decoder for performing trellis decoding on a symbol of thedetermined level; a nonsystematic Reed Solomon (NRS) decoder forperforming NRS decoding on the trellis-decoded robust data andcorrecting an error; and a restoring unit for restoring a digital videodata stream with respect to the trellis-decoded general data and theNRS-decoded robust data.

In accordance with one aspect of the present invention, there isprovided a DTV receiving method, which includes the steps of: a)receiving a transmission signal including general data and robust dataand converting the transmission signal into a base-band signal; b)determining a symbol level of the transmission signal; c) performingtrellis decoding on a symbol of the determined level; d) performingnonsystematic Reed Solomon (NRS) decoding on the trellis-decoded robustdata and correcting an error; and e) restoring a digital video datastream with respect to the trellis-decoded general data and theNRS-decoded robust data.

The following description exemplifies only the principles of the presentinvention. Even if they are not described or illustrated clearly in thepresent specification, one of ordinary skill in the art can embody theprinciples of the present invention and invent various apparatuseswithin the concept and scope of the present invention.

The use of the conditional terms and embodiments presented in thepresent specification are intended only to make the concept of thepresent invention understood, and they are not limited to theembodiments and conditions mentioned in the specification.

In addition, all the detailed description on the principles, viewpointsand embodiments and particular embodiments of the present inventionshould be understood to include structural and functional equivalents tothem. The equivalents include not only currently known equivalents butalso those to be developed in future, that is, all devices invented toperform the same function, regardless of their structures.

For example, block diagrams of the present invention should beunderstood to show a conceptual viewpoint of an exemplary circuit thatembodies the principles of the present invention. Similarly, all theflowcharts, state conversion diagrams, pseudo codes and the like can beexpressed substantially in a computer-readable media, and whether or nota computer or a processor is described distinctively, they should beunderstood to express various processes operated by a computer or aprocessor.

Functions of various devices illustrated in the drawings including afunctional block expressed as a processor or a similar concept can beprovided not only by using hardware dedicated to the functions, but alsoby using hardware capable of running proper software for the functions.When a function is provided by a processor, the function may be providedby a single dedicated processor, single shared processor, or a pluralityof individual processors, part of which can be shared.

The apparent use of a term, ‘processor’, ‘control’ or similar concept,should not be understood to exclusively refer to a piece of hardwarecapable of running software, but should be understood to include adigital signal processor (DSP), hardware, and ROM, RAM and non-volatilememory for storing software, implicatively. Other known and commonlyused hardware may be included therein, too.

Similarly, a switch described in the drawings may be presentedconceptually only. The function of the switch should be understood to beperformed manually or by controlling a program logic or a dedicatedlogic or by interaction of the dedicated logic. A particular technologycan be selected for deeper understanding of the present specification bya designer.

In the claims of the present specification, an element expressed as ameans for performing a function described in the detailed description isintended to include all methods for performing the function includingall formats of software, such as combinations of circuits for performingthe intended function, firmware/microcode and the like.

To perform the intended function, the element is cooperated with aproper circuit for performing the software. The present inventiondefined by claims includes diverse means for performing particularfunctions, and the means are connected with each other in a methodrequested in the claims. Therefore, any means that can provide thefunction should be understood to be an equivalent to what is figured outfrom the present specification.

Advantageous Effects

The present invention can improve robust data reception performance byusing parity bytes of robust data, which are used to secure backwardcompatibility, for the purpose of error correction in a DigitalTelevision (DTV) transmission system based on dual stream includinggeneral data and robust data.

DESCRIPTION OF DRAWINGS

The above and other objects and features of the present invention willbecome apparent from the following description of the preferredembodiments given in conjunction with the accompanying drawings, inwhich:

FIG. 1 is a block diagram illustrating a conventional Digital Television(DTV) transmitter; and

FIG. 2 is a block diagram describing a DTV receiver in accordance with apreferred embodiment of the present invention.

BEST MODE FOR THE INVENTION

Other objects and aspects of the invention will become apparent from thefollowing description of the embodiments with reference to theaccompanying drawings, which is set forth hereinafter. If it isconsidered that further description on the prior art may blur the pointsof the present invention, the description will not be provided.Hereinafter, preferred embodiments of the present invention will bedescribed in detail with reference to the accompanying drawings.

FIG. 2 is a block diagram describing a DTV receiver in accordance with apreferred embodiment of the present invention.

As shown, the DTV receiver 200 includes a tuner 201, an IF filter anddetector 203, an NTSC filter 205, an equalizer 207, a trellis decoder209, a data deinterleaver 211, a Nonsystematic Reed Solomon (NRS)decoder 213, a packet formatter 215, a robust deinterleaver 217, an RSdecoder 219, a data derandomizer 221, a demultiplexer 223, a synchronousand timing recovery block 230, a field synchronous decoder 232, and acontroller 234.

In particular, the DTV receiver of the present invention includes theNRS decoder 213 for performing robust data error correction ontrellis-decoded input data between the data deinterleaver 211 and thepacket formatter 215.

First, a channel for the RF signal transmitted from the transmitter 100is selected in the tuner 201 of the receiver 200. Then, the RF signalgoes through intermediate frequency (IF) filtering in an IF filter anddetector 203 and a synchronous frequency is detected. A synchronous andtiming recovery block 230 detects a synchronous signal and recovers aclock signal.

Subsequently, the signal is removed of a National Television SystemsCommittee (NTSC) interference signal through a comb filter in the NTSCfilter 205, and equalized in the equalizer 207.

For the equalizer 207, a known determiner, which is known as a slicer,or a trellis decoder with a trace back of zero (0) can be used.

The equalizer 207 equalizes a received signal based on a robust dataflag obtained from the bit-based data interleaving and the trellisinterleaving based on the ATSC A/53 and transmitted from the controller1725.

The field synchronous decoder 232 receives a segment of a data frame,restores robust data packet restoring information in a reserved area,which includes information on the rate of robust data and general datawithin a field, and information on the coding rate of the robust data,and transmits it to the controller 234.

The controller 234 computes delay between robust data and general databased on the robust data packet restoring information and transmits thedelay information to an element in need of the delay information.

Meanwhile, the data symbol removed of the multi-path interference in theequalizer 207 goes through trellis decoding in the trellis decoder 209.

The decoded data symbol is deinterleaved in the data deinterleaver 211and RS-decoded in the RS decoder 219.

Herein, the robust data additionally go through an NRS decoding processafter the data deinterleaving. That is, the NRS decoder 213 correctstransmission error by performing the NRS decoding before it removesparity bytes added to the robust data in the packet formatter 215.

As described above, RS coding gain can be acquired by using the paritybytes, which are added to the robust data to secure the backwardcompatibility of a low-ranked receiver during a transmission process,for the purpose of error correction. In accordance with the presentembodiment, an error can be corrected up to 10 bytes per 207-byte robustdata packet in a conventional channel environment.

The packet formatter 215 can remove a packet header and the parity bytesfrom the NRS-decoded robust data and reconstruct robust data which areextended into two packets into one packet.

The robust data reconstructed in the packet formatter are deinterleavedin the robust deinterleaver 217 and RS-decoded together with generaldata.

The controller computes delay time caused by the NRS decoding, thepacket formatting and the deinterleaving, which are carried out only onrobust data, and transmits the delay time information to the dataderandomizer 221.

The data derandomizer 221 derandomizes the general data and the robustdata based on the transmitted delay time. For example, when the n^(th)general data packet is derandomized, the next robust data packet to bederandomized may not be the (n+1)^(th) robust data packet transmittedfrom the transmitter but it may be the k^(th) robust data packet wherek<n. A robust data packet is delayed behind a general data packet due todelay in restoration into the original packet in the packet formatter215. Therefore, the data derandomizer 221 should perform thederandomization in consideration of the delay.

The demultiplexer 223 demultiplexes general and robust data packetsbased on the robust data flag to thereby output a serial data streamformed of 188-byte MPEG compatible data packets.

While the present invention has been described with respect to certainpreferred embodiments, it will be apparent to those skilled in the artthat various changes and modifications may be made without departingfrom the scope of the invention as defined in the following claims.

1. A Digital Television (DTV) receiver, comprising: a receiving unit forreceiving a transmission signal including general data and robust dataand converting the transmission signal into a base-band signal; anequalizing unit for determining a symbol level of the transmissionsignal; a trellis decoding unit for performing trellis decoding on asymbol of the determined level; a nonsystematic Reed Solomon (NRS)decoding unit for performing NRS decoding on the trellis-decoded robustdata and for performing robust data error correction on thetrellis-decoded robust data; and a restoring unit for restoring adigital video data stream with respect to the trellis-decoded generaldata and the NRS-decoded robust data.
 2. The DTV receiver as recited inclaim 1, wherein the restoring unit includes: a packet formatting unitfor reconstructing a packet with respect to the robust data; a datadeinterleaving unit for deinterleaving the reconstructed robust data; anRS decoding unit for correcting a forward error with respect to thegeneral data and the robust data; and a data derandomizing unit forderandomizing the RS-decoded data.
 3. The DTV receiver as recited inclaim 2, wherein the restoring unit further includes a controller forcomputing a delay time that is the delay between the robust data and thegeneral data, the delay time including delay caused by NRS decoding andpacket reconstruction, and the data derandomizing unit performsderandomization in consideration of the delay time.
 4. The DTV receiveras recited in claim 1, wherein the NRS decoding is performed beforeparity bytes, which are added to the robust data to secure backwardscompatibility, are removed.
 5. A Digital Television (DTV) receivingmethod, comprising: receiving a transmission signal including generaldata and robust data and converting the transmission signal into abase-band signal; determining a symbol level of the transmission signal;performing trellis decoding on a symbol of the determined level;performing nonsystematic Reed Solomon (NRS) decoding on thetrellis-decoded robust data and performing robust data error correctionon the trellis-decoded robust data; and restoring a digital video datastream with respect to the trellis-decoded general data and theNRS-decoded robust data.
 6. The method as recited in claim 5, whereinrestoring the digital video data stream comprises: reconstructing apacket with respect to the robust data; deinterleaving the reconstructedrobust data; performing forward error correction with respect to thegeneral data and the robust data; and derandomizing the RS-decoded data.7. The method as recited in claim 6, wherein restoring the digital videodata stream further comprises: computing delay time for NRS decoding andpacket reconstruction with respect to the robust data, andderandomization is performed in consideration of the delay time in thederandomizing of the RS-decoded data.